As reported in our blog last week, Cyclone Chapala formed in the Arabian Sea and became the second strongest cyclone on record in this region with estimated peak winds averaged over one minute of 155 mph. Only Cyclone Gonu in 2007 was more intense. Since then Chapala has weakened slightly, but still has winds in excess of 100 mph.

Chapala has been moving westwards and is now moving into the Gulf of Aden. Landfall is expected over Yemen early on Tuesday 3 November UK time with winds still expected to be at least of hurricane strength (75 mph or more). This region has climatologically very low annual rainfall totals (approximately 50 mm), but could receive several times this amount from the cyclone, which raises the possibility of flash flooding in areas not used to much rain. Although central and eastern Yemen has a relatively sparsely populated coastline, the city of Al Mukalla is close to the projected location of landfall.

Cyclone Chapala at 1230 UTC on 02 November 2015

The Arabian Sea normally only produces three or four tropical cyclones per year at most. Some years there are no cyclones at all and often they do not reach hurricane strength. Thus for a cyclone of this intensity to be moving directly into the Gulf of Aden with a likely landfall over Yemen is a rare event – but is it unprecedented?

Records back to the 1980s show that no tropical cyclones of tropical storm intensity or greater (winds over 39 mph) have made landfall over Yemen. However, in 2008 a tropical depression did cross the coast. Although winds were not strong, it brought heavy rain, flooding and caused many fatalities in Yemen.

To the east of Yemen, the neighbouring country of Oman has seen several landfalls of tropical cyclones. In 2002 a weak tropical storm made landfall just on the Oman side of the border with Yemen. The two strongest cyclones to make landfall over Oman were Gonu (2007) and Phet (2010), but both of these were over the north of the country well away from where Chapala is located.

For a tropical cyclone to navigate directly into the Gulf of Aden takes a very precise track. The most recent to do this was Bandu in 2010, but it was weak and dissipated without making landfall.

Records prior to the 1980s are considered less reliable due to poor satellite data coverage, but there are a few examples of storms which entered the Gulf of Aden. There is sparse detail of cyclone intensities this far back, but no evidence of any which entered the Gulf of Aden or made nearby landfall at an intensity as high as that currently exhibited by Cyclone Chapala.

Therefore, using the historical information available it can be concluded that Chapala is the strongest cyclone on record to enter the Gulf of Aden and will likely be the strongest on record to make landfall over Yemen if current forecasts are correct.

Official warnings for the latest tropical cyclones in the Arabian Sea are produced by the India Meteorological Department. The Met Office routinely supplies predictions of cyclone tracks from its global forecast model to regional meteorological centres worldwide, which are used along with guidance from other models in the production of forecasts and guidance. We also provide updates on current tropical storms via @metofficestorms on Twitter.

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